How to distinguish: Sturgeon or Gar

[PaleoNoel]

Hi everyone, I was wondering how one would distinguish the armor skull plates of a gar with some of the osteoderms found on sturgeon. I have definitely found the former but cannot be certain if I've found the prior. From looking at some pictures online I see similarity between the two and wondered if I had any in my collection and if I could properly identify a fossil as sturgeon as opposed to gar.